The US State Department has offered up to $10 million ($15.3 million) for information on the "Blackcat" ransomware gang who hit the UnitedHealth Group's tech unit and snarled insurance payments across America.
"The ALPHV Blackcat ransomware-as-a-service group compromised computer networks of critical infrastructure sectors in the United States and worldwide," the department said in a statement announcing the reward offer.
UnitedHealth said last week it was beginning to clear a medical claims backlog of more than US$14 billion as it brought its services back online following the cyber attack, which caused wide-ranging disruption starting in late February.
UnitedHealth's tech unit, Change Healthcare, plays a critical role in processing payments from insurance companies to practitioners, and the outage caused by the cyber attack has in some cases left patients and doctors out of pocket.
The toll on the community health centres that serve more than 30 million poor and uninsured patients has been especially harsh.
Hackers said earlier this month that UnitedHealth paid a US$22 million ransom in a bid to recover its systems, but whether Blackcat honoured its end of the bargain has not been made public.
Shortly after the hack, the group put a bogus press release on its website falsely claiming it had been seized by law enforcement, giving the impression that they had shut down operations.
